DTCAP-a distributed tunable-channel access protocol for multi-channel photonic dual bus networks

In a multi-channel photonic dual bus network, each unidirectional bus contains a number of channels (wavelengths) and the bus headend periodically generates fixed length slots on each of the channels. Generally, one channel called the control channel is used to carry signals and the others are data channels. Each station is equipped with one-fixed-transmitter and one fixed-receiver which are permanently tuned to the dedicated control channel, and n tunable-transmitters and m tunable-receivers are tunable over the entire wavelength range. For non-overlapping traffic in the network, the maximum network throughput will be achieved by applying the wavelength reusing concept. Given a set of serving traffic, a set of new traffic requests, and c data channels (wavelengths), the wavelength/receiver assignment problem ((n, m, c)-WRAP) is to assign a transmission wavelength and a receiver for each request such that the network throughput is maximized and the number of assigned wavelengths is minimized. In this paper, we prove that the (n, m, c)-WRAP is NP-hard. An efficient distributed tunable-channel access protocol (DTCAP) is proposed for the (1, m, c)-WRAP. Based on the DTCAP, three different schemes are proposed for assigning the wavelength/receiver. The performance of the three proposed schemes on the DTCAP are evaluated and compared by simulation. Simulation results demonstrate that for a limited number of wavelengths and receivers, the proposed schemes substantially improve the network throughput and access delay under general traffic demands